I installed the basic system on vmware.
After i partitioned and setup the basic system by stage3.xxx I setup
the grub. As you know i have to use the "modprobe sd_mod" to activate the virtual drive. It said that I have a scsi hard drive so I should installed the gentoo in the /dev/sda1 and swap in the /dev/sda2.

But when I setup the grub, I should write like this
Grub > root (hd0,0)

not

Grub > root (sd0,0)

I don't know why I should tell the "hd0" for root partitoin.

And the real problem is I can't mount the root filesystem.
After the kernel is decompressed and it shoud try to mount the
root file system. But it said that

I change the virtual disk type from SCSI to IDE then I found the hda
is used in vmware.

Is this the same as selecting install a FreeBSD guest OS instead of Linux? I am fighting the same problem for days now w/ VMware 3.1/WXP. I don't see another possibility of switching away from SCSI for Linux guests, or is there one?

I think you have the same problem I had.
I don't know if it is possible to change the Virtual disk type from SCSI to IDE. I just delete the virual disk and create a new one. After I create a new one, I change the Virtual disk type in the vmware. When you launch the vmware you can see the created the virtual disk in the left panel of vmware. And you can change the all hardware properties by clicking the virtual disk with right button such as changing properties in the normal windows program.
Maybe the SCSI is selected and IDE is disabled. Just change it.